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Hostile computer attacks are classed among the most serious threats to national security

Attacks on computer networks are among the biggest emerging threats to the UK, according to the new national security strategy. But how does it compare to other national defence reviews?

National defence reviews in Britain are famous for providing cover for cuts in national defence spending.

They normally just catch up with the fact that Britain cannot afford to do, or even wants to do, as much as it did.

This one is not much different. Everyone knows that the government wants to save money. Defence is an obvious target.

However, in advance of the cuts, which will be announced on Tuesday, comes the so-called strategy. It is called A Strong Britain in an Age of Uncertainty.

'A bit evasive'

The government has used a risk assessment technique along with the accompanying jargon (the "ends, the ways and the means") to arrive at a kind of league table of risks.

They are in three tiers.

In the top tier of four threats are international terrorism (meaning mainly al-Qaeda, but including Northern Irish dissident threats as well), cyber attacks, a major accident or natural disaster and the more conventional international military crisis in which the UK might intervene.

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The Falklands War followed a downsizing of the Royal Navy ordered in 1981

The second tier includes instability anywhere in the world that could produce a threat (Afghanistan, of course, is the current example).

And there is a third tier which collects together an assortment including the disruption of vital supplies and an attack on a UK territory (the Falklands comes to mind). In this category, the actual risk of attack is considered low.

British officials acknowledge that the selection of risks is partly a matter of judgement.

Indeed, past reviews have failed to predict crises. In 1981 the Royal Navy was ordered to lose ships only to find itself fighting the Falklands War the following year.

This review is different in that, claiming to unite thinking about both defence and security, it widens the nature of the threats to give priority to non-conventional ones.

7/7 bomb attacks

The concentration on non-conventional threats immediately raises the question whether the government will give more money to these areas. If these threats are as serious as stated, then this might be expected.

After all, the security service MI5 blamed a lack of resources to justify its decision not to follow Mohammad Sidique Khan, the leader of the 7/7 London bombers, when he was spotted meeting another suspected terrorist group under surveillance.

If he had been followed, the London bombings might have been averted.

The strategy document is a bit evasive about this. It states that the counter-terrorist capability will be "protected" (but does that mean it could be expanded?) and that although some risks are higher than others, "this does not automatically mean that greater resources must be allocated to them".

A special BBC News season examining the approaching cuts to public sector spending

We might therefore end up having a league table of risks in which the greatest risk (and Prime Minister David Cameron in a foreword calls al-Qaeda the "most pressing threat") is not properly funded.

On the wider defence front, there will be critics who say that Britain's retention of major weapons systems - particularly the expected building of two aircraft carriers albeit probably with fewer planes to fly on them - means the temptation to intervene with force in some crisis will still be present.

Supporters of a British world role, especially in Nato, will be pleased that a substantial capability has been maintained.

At the same time they usually try to justify some continuing worldwide military role.

They share out the cuts among the services, mostly after a huge political battle, in such a way that rarely is there a huge change in policy - more a paring down of capability reflecting the relative decline of British economic power.

Only occasionally do you see a major lurch, as in the withdrawal from East of Suez in 1968 or the downsizing of the Royal Navy ordered in 1981.

The latter was, of course, promptly followed by the Falklands War, bringing down much criticism on the policy.

There is no major lurch this time. The thinking is laid out in a document called the National Defence Strategy. It will be followed by the actual spending announcements on Tuesday.